KjetilK writes: "The W3C just gave SPARQL the stamp of approval. SPARQL is a query language for the Semantic Web, and differs from othe query languages in that is usable across different data sources. There are allready 14 implementations of the spec, which is a lot. Most of them are free software. There are also billions of relations out there that are queryable, thanks to the Linking Open Data project. The structured data of Wikipedia are now queryable at DBpedia. Also, have a look at Ivan Herman's presentations.